1. Field of the Invention
The present invention relates to an analog-to-digital converter. More particularly, the present invention relates to an analog-to-digital converter circuit using current mixing which increases exponentially.
2. Description of the Related Art
A Digital-to-Analog Converter (DAC), which may also be referred to as an analog-to-digital converter, is a circuit for converting an n-bit input digital signal into an analog signal, and is an element that is widely used in applications including instrumentation, control, communication, imaging, and other similar electronic devices.
FIG. 1 depicts a method for converting a digital signal to an analog signal according to the related art.
Referring to FIG. 1, when a 2-bit digital signal is input, a current corresponding to 2-bit digital information flows to output an analog signal. A general linear DAC converts the 2-bit digital signal that is uniformly quantized into the analog value as shown in FIG. 1. To generate a weak signal within a quantization noise, as shown in the bottom left area of FIG. 1, bits need to be expanded to increase steps. For example, a 4-step quantization may be controlled with 2 bits and its Dynamic Range (DR) or resolution is 13.8 dB. When the bits are extended to 3 bits, the DR of 19.82 dB is attained. In theory, as the number of the bits increases by one bit, the DR increases by 6.02 dB for each increased bit.
Analog signals, such as sound, light, vibration, concentration, or any other similar and/or suitable analog value, in the natural word may change in a non-linear manner, and instead, may have exponential change rates, and sensory systems of humans may have logarithmic characteristics for sensing the exponential changes. For example, in the case of analog audio signals, whispers may be quite audible in a quiet room, whereas a loud voice may be inaudible in a noisy place next to an aircraft engine. Such characteristics of analog audio signals are due to a human auditory system having logarithmic characteristics which are sensitive to the weak signal but insensitive to the strong signal, and this is also applied to image information input to human eyes. Hence, a decibel dB unit is used by taking a logarithmic value from the absolute value of such analog signals, such as the naturally occurring signals of sound and light, and multiplying the logarithmic value by 20.
Accordingly, high-fidelity devices may be maximized up to the sensitive range of human sensory systems in order to have a high DR, i.e. resolution, which generally ranges from 80 dB to 120 dB. The sensory range of 80 dB to 120 dB may be converted to generate digital information values ranging from 16 bits to 24 bits, and thus, a data size may increase for such high-fidelity devices. That is, even a strong signal that may relatively insensitive may be finely quantized by high-fidelity devices so as to cause inefficiency.
Therefore, a need exists for a system and method for a DAC for converting the digital signal to the non-linear analog signal with high fidelity without increasing a digital code.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present invention.